A digitizing tablet (or digitizer) has an operation panel (or a touch panel) which is supported by a support substrate. An indicator such as a stylus pen or a finger is positioned at an input position as it contacts or is in close proximity to the operation panel. Data relating to the detection of the input position is transmitted to a processing device such as a personal computer.
Components such as the operation panel, the support substrate, an insulating layer, and electrodes may be transparent. Therefore, the digitizing tablet may be disposed on a display screen such as a liquid crystal panel or CRT. An input can be received via the input surface of the operation panel of the digitizing tablet with reference to the display on the display screen. The input position data associated with the location of the input relative to the display on the display screen can be delivered to the processing device.
Typical digitizing tablets are classified according to their methods for detecting input positions relative to the operation panel. Japanese Patent Laid-Open Publication No. Hei 5-289806 discloses the electromagnetic coupling method; Japanese Patent Laid-Open Publication No. Hei 6-242875 discloses the capacitive coupling method; Japanese Utility Model Laid-Open Publication No. Hei 3-6731 discloses the touch method; Japanese Patent Laid-Open Publication No. Hei 5-53715 discloses the resistive method; and Japanese Utility Model Laid-Open Publication No. Hei 5-33235 discloses the optical coupling method. However, the operator must check a processing device such as a personal computer when using these methods to verify that the input was received successfully. Therefore, the operator does not know if the input on the operation panel has been detected by the digitizing tablet.
A force feedback tablet vibrates the operation panel or the support substrate so that the operator can feel the vibration via a stylus pen or a finger that is in contact with the operation panel. The force feedback tablet provides feedback to the operator when an input touch has been detected by the digitizing tablet.
FIG. 9 shows a typical force feedback tablet 100. The force feedback tablet 100 has a main tablet body 100A which includes an operation panel 101, a plastic sheet 102, and a support substrate 103. The operation panel 101 is made of a plastic flexible sheet, and the support substrate 103 is made of glass. A plastic sheet 102 is affixed to the surface of the support substrate 103 which is opposite to the operation panel 101. The operation panel 101 is spaced slightly apart from the support substrate 103, and multiple insulating projections 104 are interposed between the operation panel 101 and the support substrate 103.
The force feedback tablet 100 is a resistive digitizing tablet with an electrically conductive layer (not shown) of a uniform resistive film formed on the opposing surfaces of the operation panel 101 and the plastic sheet 102. The electrically conductive layers contact each other and provide electrical conduction at the input position when the input in the form of a touch is transmitted to the surface of the operation panel 101. The lead electrodes (not shown) are connected electrically to the periphery of the electrically conductive layers to detect the input position.
Truncated conical cushion mounts 106 are provided on the bottom surface of a housing 105 and support the support substrate 103. The entire main tablet body 100A is placed on the cushion mounts 106 made of rubber having a hardness of 50 to 60 degrees. The cushion mounts 106 must be hard enough to provide sufficient resistance to the input touch on the operation panel 101.
A display panel 107 is disposed between the housing 105 and the support substrate 103 which is supported on the cushion mounts 106. Each of the components formed on the support substrate 103 are transparent so that the display appearing on the display panel 107 can be seen when viewed from above the operation panel 101.
A piezoelectric actuator 108 is located at an edge of the rear surface of the support substrate 103. The piezoelectric actuator 108 comprises a plurality of piezoelectric substrates stacked in layers and is made of a piezoelectric material such as piezoelectric ceramic. The piezoelectric actuator 108 vibrates due to the electrostrictive effect of the piezoelectric substrate and serves as a vibration source when a drive voltage is applied to the piezoelectric substrate.
The proximal end of the piezoelectric actuator 108 is fixed to a support base 109, and a support shaft 110 rotatably supports the intermediate portion of the piezoelectric actuator 108. A contact 111 is fixed to the distal end of the piezoelectric actuator 108 and contacts the rear surface of the support substrate 103.
Pressing a position for the input touch on the operation panel 101 will cause the electrically conductive layers to contact each other at the input position. The input position detection means (not shown) detects the input and the input position in order to deliver the data corresponding to the input position to a processing device such as a personal computer.
A drive voltage is applied to the drive electrodes of the piezoelectric actuator 108 causing the piezoelectric actuator 108 to vibrate when the input is detected. The vibration is transmitted to the support substrate 103 via the contact 111 disposed at the distal end of the piezoelectric actuator 108 so that the finger pressing the operation panel 101 senses the vibration.
The operator can verify from the vibration that the input touch has been accomplished successfully after providing the input touch to the digitizing tablet.
The conventional digitizing tablet employs a vibrating element such as a piezoelectric actuator, a vibration motor, and the like as its vibration source in order to vibrate the operation panel 101 or the support substrate 103. The vibration source is separate from the operation panel 101 and the support substrate 103 which constitute the digitizing tablet. Therefore, the housing 105 and the entire input device is larger in order to accommodate the separate vibration source, and the design of the outer shape needs to be limited.
Additionally, the piezoelectric actuator 108, acting as the vibration source, must produce sufficiently large displacements in order to transmit a vibration that can be detected on the main tablet body 100A which contacts the piezoelectric actuator 108. Therefore, a plurality of piezoelectric substrates are stacked in layers in the piezoelectric actuator 108. The layers of piezoelectric substrates increase the thickness of the piezoelectric actuator 108. Furthermore, a pair of drive electrodes are affixed to each piezoelectric substrate and are stacked in the direction of thickness of the piezoelectric actuator 108. The manufacturing process of stacking the layers of piezoelectric substrates requires many steps and is expensive.
Furthermore, a vibration motor is large and expensive if employed as the vibration source.
It is difficult to transmit the vibrations from the vibration source to the main tablet body 100A since the vibrations are indirect and originate from vibration sources which are separate from the main tablet body 100A. The main tablet body 100A is unable to convey precise changes in vibration frequency for transmitting different types of information to the operator, thereby making it impossible to transmit information accurately.
It is difficult to transmit exact changes in vibration directly to the main tablet body 100A since there is a delay in transmitting the vibration from the vibration source to the main tablet body 100A.
The drive circuit for driving the vibration source must include an oscillation circuit so that the vibration source such as the piezoelectric actuator 108 or the vibration motor can vibrate continuously for a certain period of time. This oscillation circuit complicates the drive circuit. A vibration source such as a vibration motor cannot be activated by a drive voltage with an instantaneous pulse waveform and requires a drive circuit having an activation control function to operate continuously for a certain period of time. A vibration source such as the piezoelectric actuator 108 contracts and expands instantaneously in response to the application of a drive voltage with an instantaneous pulse waveform. However, the contraction and expansion is damped when transmitted to the main tablet body 100A, thereby making it impossible for the operator to sense vibration instantaneously.
Securing the piezoelectric actuator 108 to the housing 105 requires a complicated structure for rotatably supporting the intermediate portion of the piezoelectric actuator 108 on the support shaft 110 and for supporting the end of the piezoelectric actuator 108 on the support base 109. The piezoelectric actuator 108 vibrates or generates a noise if not attached securely, thereby making it impossible to transmit the vibration to the main tablet body 100A.
Furthermore, the configuration of the piezoelectric actuator 108 and a vibration transmission mechanism of the main tablet body 100A, such as the support substrate 103, must be manufactured accurately. A gap between the contact 111 and the support substrate 103 would generate noise and vibrations that can damp the amplitude of the vibrations intended for the operator.
Digitizing tablets employing the magnetic coupling method, the capacitive coupling method, and the optical coupling method do not require an indicator such as a stylus pen or the operator's finger to physically contact the operation panel. It is impossible to transmit vibrations to the operator through the operation panel or the support substrate in order to indicate the detection of the input on the digitizing tablet.